1. Field of Invention
The present invention relates to a method for calibrating an optical arrangement.
2. Description of Related Art
The present invention refers to a method for calibrating an optical arrangement in respect to a global coordinate system. The optical arrangement includes a carrier unit made of a rigid material, an optical acquiring unit and a light emitting unit both releasably connected to the carrier unit. Such an optical arrangement is known from DE 10311247 A1, for example, wherein the carrier unit has a profile with a U-shaped cross section that profile can be cut and folded from a metal sheet. The light emitting unit and/or the optical acquiring unit each include a housing element, which is formed in such a way that it can be inserted into the inside of the profile from an open side of the profile and disposed therein, preferably free from float or play. The profile includes holes for receiving screws and the housing of the optical acquiring unit and the light emitting unit, respectively, have threaded holes for receiving the screws put through the holes of the profile. In order to releasably fasten the optical acquiring unit and the light emitting unit, respectively, to the profile, fastening screws are inserted into the holes and screwed into the threaded holes.
This kind of fastening enables a high precision fastening of the optical acquiring unit and the light emitting unit, respectively, to the carrier unit. However, after loosening the screwed connections, the housings can be moved inside the profile and, when tightening the screws again or after having inserted another optical acquiring or light emitting unit to the carrier unit, it cannot be ensured that the optical acquiring unit and the light emitting unit, respectively, are still and will be fixed in exactly the same position in respect to the carrier unit as they were before. Thus, the type of connection taught in the prior art is not repeatable.
Therefore, in the prior art, first the optical acquiring unit and the light emitting unit are connected and fixed to the carrier unit in any desired position. Then the entire optical arrangement has to be calibrated in respect to a global coordinate system. The global coordinate system can be assigned to a single optical arrangement or to a measuring arrangement, for example a measuring tunnel, including a plurality of optical arrangements of the above-identified kind. The calibration has to be performed prior to the first use of the optical arrangement and thereafter each time one of the optical acquiring or light emitting units has been exchanged or has deliberately or unintentionally changed its position in respect to the carrier unit. The necessity of calibrating the entire optical arrangement has the disadvantage that calibration has to take place inline (during an interruption of the optical arrangement's intended use). Furthermore, the calibration of the optical arrangement according to the prior art is very complicated, cumbersome, and time consuming.
Therefore, it is an object of the present invention to suggest a method for calibrating an optical arrangement which is easy, fast and, in particular, can be performed offline, that is during the intended use of the optical arrangement.